Dense Slurry Production Methods and Systems

ABSTRACT

Methods and systems for producing a dense oil sand slurry from subsurface reservoirs are provided. The methods include reducing pressure at a producer pipe inlet to draw a dense slurry into the producer pipe using a jet pump, generating a diluted dense slurry using the jet pump, and lifting the diluted dense slurry through the producer pipe utilizing a slurry lift apparatus, which may be a fluid lift apparatus. The systems include a producer pipe into an oil sand reservoir, a jet pump configured to generate a low pressure region around the opening of the producer pipe to draw the dense slurry into the producer pipe and dilute the dense slurry to form a diluted dense slurry; and a gas lift apparatus configured to lift the diluted dense slurry through the producer pipe towards the surface of the earth.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication 61/238,564 filed 31 Aug. 2009 entitled DENSE SLURRYPRODUCTION METHODS AND SYSTEMS, the entirety of which is incorporated byreference herein.

FIELD OF THE INVENTION

Embodiments of the invention relate to methods and systems for producinga dense oil sand slurry. More particularly, embodiments of the inventionrelate to methods and systems for artificially lifting dense oil sandslurries from oil sand formations located in a subsurface formationhaving an overburden.

BACKGROUND

This section is intended to introduce various aspects of the art, whichmay be associated with exemplary embodiments of the present disclosure.This discussion is believed to assist in providing a framework tofacilitate a better understanding of particular aspects of the presentdisclosure. Accordingly, it should be understood that this sectionshould be read in this light, and not necessarily as admissions of priorart.

Bitumen is any heavy oil or tar with viscosity more than 10,000 cP foundin porous subsurface geologic formations. Bitumen is often entrained insand, clay, or other porous solids and is resistant to flow atsubsurface temperatures and pressures. Current recovery methods injectheat or viscosity reducing solvents to reduce the viscosity of thebitumen and allow it to flow through the subsurface formations and tothe surface through boreholes or wellbores. Other methods breakup thesand matrix in which the heavy oil is entrained by water injection toproduce the formation sand with the oil; however, the recovery ofbitumen using water injection techniques is limited to the area proximalthe bore hole. These methods generally have low recovery ratios and areexpensive to operate and maintain. However, there are hundreds ofbillions of barrels of these very heavy oils in the reachable subsurfacein the province of Alberta alone and additional hundreds of billions ofbarrels in other heavy oil areas around the world. Efficiently andeffectively recovering these resources for use in the energy market isone of the world's toughest energy challenges.

Extracting bitumen from oil sand reservoirs generally leads toproduction of sand, limestone, clay, shale, bitumen, asphaltenes, andother in-situ geo-materials (herein collectively referred to as sand orparticulate solids) in methods such as Cold Heavy Oil Production withSand (CHOPS), Cyclic Steam Stimulation (CSS), Steam Assisted GravityDrainage (SAGD), and Fluidized In-situ Reservoir Extraction (FIRE). Theamount of sand and water produced may vary from very small to large andit depends on the type of method, stress-state within the reservoir,drawdown and depletion. In cases of CSS and SAGD, sand production is notdesirable. On the other hand, sand production is encouraged in cases ofCHOPS and FIRE (International Patent Application PublicationWO2007/050180) processes. When the amounts of sand and water producedare very large, it is important to be able to safely dispose the sandand water back into subsurface.

Various artificial lift (“AL”) methods for lifting oil/water/gas withsome small solids content is known in the oil industry. However, liftinga dense slurry through a vertical pipe represents a unique challenge dueto large slurry resistance components such as friction and hydrostaticpressure. Reactions of sand in a slurry in a motive state (having avelocity distribution) may be determined by its rheology expressed by astress (τ) to strain rate ({dot over (γ)}) relationship. One example ofsuch a relationship is the Herschel-Bulkley model: τ=τ_(y)+K{dot over(γ)}″. For a dense slurry, an increase in production rate (velocity) byβ times could result in a frictional stress increase by a factor of β″,n≈1.5÷2. As such, a sufficiently powerful artificial lift (“AL”)apparatus should be employed to circumvent the frictional pressure dropincrease β″ associated with the friction increase.

Another issue with using existing AL approaches to lift dense slurriesis the high erosion rate. A dense slurry has very high sand contentcharacterized by high erosive power characteristic of sand particles.The erosion problem is augmented by the duration of the lift process andcost and necessity to shut down the producer well associated withunderground pump maintenance. In short, current AL methods are notcapable of lifting such a dense slurry from any substantial depth overan extended period of time.

Jet pumps have been used in the oil and gas industry for a variety ofapplications. For example, U.S. Pat. No. 6,821,060 to McTurk et al.(“McTurk”) describes application of a jet pump in an oil sand miningoperation. In particular, a mined and crushed oil sand is fed into a jetpump via a hopper to form a “conditioned,” aqueous oil sand slurry. In asimilar application, U.S. Pat. No. 6,527,960 to Bacon et al. (“Bacon”)describes a method of treating mined oil sands using a jet pump scrubberto remove the oily film from the tar sand particulates. Neither McTurknor Bacon contemplate the use of a jet pump for producing the oil sandsfrom a formation.

A different example of jet pumps in mining operations is disclosed inU.S. Pat. No. 4,527,836 to Uhri (“Uhri”). In Uhri, the jet pump isplaced in an oil shale formation where the nozzle of the water jet isdirected outwardly to cut chunks of oil shale from the formation. See,e.g. Uhri at FIG. 1 and col. 3, 11. 27-29. Uhri does not disclose use ofa jet pump to produce a slurry by moving it into a wellbore.

Jet pumps have also been used in various oil field operations. Forinstance, U.S. Pat. No. 7,063,161 to Butler et al. (“Butler”) describesthe use of a jet pump with a motive fluid containing some gas to producecrude oil from a well bore. Butler does not disclose or contemplateproducing solids laden slurries. In another application, U.S. Pat.Application No. 2005/0121191 to Lambert et al. (“Lambert”) describes theuse of a jet pump with increased erosion protection to lift slurry fromthe wellbore during a cleanout workover in an oil well. The idea is tooperate jet with very large pressure drop as motive fluid exits the jetand mixes with slurry to induce cavitation to lower erosion rates in thethroat entrance. However, Lambert does not contemplate producing fluidsfrom a formation or producing a dense slurry.

What is needed are methods and systems capable of lifting dense slurriesfrom subsurface formations for production.

Other relevant material may be found in: U.S. Pat. No. 7,200,539; U.S.Pat. App. No. 2003-0201098; CA Pat. No. 2,582,091; ACKERMAN NL, HUNG TS,Rheological characteristics of solid-liquid mixtures, A. I. Ch. E.Journal, 25 2, 327-332 (1997); JACOBS BEA, Design of Slurry TransportSystems, Taylor and Francis, London and New York, ISBN 1-85166-634-6,71-101 (2006); Li J, MISSELBROOK JG AND SEAL J, Sand cleanout withcoiled tubing: choices of process, tools or fluids, SPE 113267 (2008);HEYWOOD NI AND CHARLES ME, Effects of gas injection on the vertical pipeflow of fine slurry, Proc. Hydrotransport 7 Conf., Paper El, BHRA,Sendai, Japan, (Nov 4-6 1972); ODROWAZ-PIENIAZEK S, Solids-handlingpumps—a guide to selection, The Chemical Engineer, (February 1979);MANGESANA N, CHIKUKU RS, MAINZA AN, GOVENDER I VAN DER WESTHUIZEN AP ANDNARASHIMA M, The effect of particle sizes and solids concentration onthe rheology of silica sand based suspensions, Journal of the SouthernAfrican Institute of Mining and Metallurgy, 108, 237-243 (2008);WAKEFIELD A W, The jet-pump scrubber, Quarry Management, (February1993); WANG X, Zou H, Li G, NIE C, CHEN J, Integrated well-completionstrategies with CHOPS to enhance heavy-oil production: a case study inFula oilfield, SPE 97885 (2005); WILLIAMS S, Rozo R, AYA F P, HERNANDEZJIS, Artificial lift optimization in the Orito field, SPE 116659 (2008);WILSON G, The design aspects of centrifugal pumps for abrasive slurries,Proc. Hydrotransport 2 Conf., Paper H2, BHRA, Cranfield (1972).

SUMMARY OF THE INVENTION

In one embodiment of the present disclosure, a method for producing adense slurry is provided. The method includes reducing a pressure at aproducer pipe inlet to draw the dense slurry into a producer pipe from asubsurface formation, wherein the pressure is reduced using a jet pumpto direct a power fluid towards the producer pipe inlet at an initialflow rate; generating mixing the power fluid and the dense slurryutilizing the jet pump to form a diluted dense slurry using the jetpump; flowing the diluted dense slurry into the producer pipe at an theinitial flow rate; and lifting the diluted dense slurry through theproducer pipe utilizing a slurry lift apparatus. The slurry liftapparatus may be a fluid or gas lift apparatus, a progressive cavitypump, an electric submersible pump, or any combination of these.

In a second embodiment of the present disclosure, a system for producinghydrocarbons is provided. The system includes a well bore containing aproducer pipe extending through an overburden below a surface of theearth into an oil sand reservoir, the producer pipe having an at leastone opening configured to permit the flow of a dense slurry into theproducer pipe from the oil sand reservoir; a jet pump incorporated intothe well bore configured to inject a power fluid at a rate sufficient togenerate a low pressure region around the at least one opening of theproducer pipe to draw the dense slurry from the oil sand reservoir intothe producer pipe and dilute the dense slurry to form a diluted denseslurry; and a slurry lift apparatus configured to lift the diluted denseslurry through the producer pipe towards the surface of the earth. Theslurry lift apparatus may be a fluid or gas lift apparatus, aprogressive cavity pump, an electric submersible pump, or anycombination of these.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the present invention may becomeapparent upon reviewing the following detailed description and drawingsof non-limiting examples of embodiments in which:

FIG. 1 is a process flow chart for methods of producing a dense slurryin accordance with certain aspects of the disclosure;

FIG. 2 is an illustration of one exemplary embodiment of the artificiallift system used in the process of FIG. 1 using a fluid lift apparatusto provide slurry lift;

FIG. 3 illustrates an alternative exemplary embodiment of the artificiallift system of FIG. 2;

FIGS. 4A-4C illustrate four additional exemplary embodiments of theartificial lift system of FIG. 2; and

FIGS. 5A-5B illustrate alternative exemplary embodiments of theartificial lift method of FIG. 1 and system of FIG. 2 utilizing pumps toprovide slurry lift.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description section, the specific embodimentsof the present disclosure are described in connection with preferredembodiments. However, to the extent that the following description isspecific to a particular embodiment or a particular use of the presentdisclosure, this is intended to be for exemplary purposes only andsimply provides a description of the exemplary embodiments. Accordingly,the disclosure is not limited to the specific embodiments describedbelow, but rather, it includes all alternatives, modifications, andequivalents falling within the true spirit and scope of the appendedclaims.

DEFINITIONS

Various terms as used herein are defined below. To the extent a termused in a claim is not defined below, it should be given the broadestdefinition persons in the pertinent art have given that term asreflected in at least one printed publication or issued patent.

The terms “a” and “an,” as used herein, mean one or more when applied toany feature in embodiments of the present inventions described in thespecification and claims.

The use of “a” and “an” does not limit the meaning to a single featureunless such a limit is specifically stated.

The term “about” is intended to allow some leeway in mathematicalexactness to account for tolerances that are acceptable in the trade.Accordingly, any deviations upward or downward from the value modifiedby the term “about” in the range of 1% to 10% or less should beconsidered to be explicitly within the scope of the stated value.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

The term “dense slurry,” as used herein, refers to a mixture of solidsand fluids having a solids concentration range of about 30-65 volumepercent (vol %). Such a dense slurry may be found naturally in-situ, maybe generated by the FIRE process, or may be generated by anotherprocess.

The term “exemplary” is used exclusively herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

The term “formation” refers to a body of rock or other subsurface solidsthat is sufficiently distinctive and continuous that it can be mapped. A“formation” can be a body of rock of predominantly one type or acombination of types. A formation can contain one or morehydrocarbon-bearing zones. Note that the terms “formation,” “reservoir,”and “interval” may be used interchangeably, but will generally be usedto denote progressively smaller subsurface regions, zones or volumes.More specifically, a “formation” will generally be the largestsubsurface region, a “reservoir” will generally be a region within the“formation” and will generally be a hydrocarbon-bearing zone (aformation, reservoir, or interval having oil, gas, heavy oil, and anycombination thereof), and an “interval” will generally refer to asub-region or portion of a “reservoir.”

The term “heavy oil” refers to any hydrocarbon or various mixtures ofhydrocarbons that occur naturally, including bitumen and tar. In one ormore embodiments, a heavy oil has a viscosity of between 1,000centipoise (cP) and 10,000 cP. In one or more embodiments, a heavy oilhas a viscosity of between 10,000 cP and 100,000 cP or between 100,000cP and 1,000,000 cP or more than 1,000,000 cP at subsurface conditionsof temperature and pressure.

The term “hydrocarbon-bearing zone,” as used herein, means a portion ofa formation that contains hydrocarbons. One hydrocarbon zone can beseparated from another hydrocarbon-bearing zone by zones of lowerpermeability such as mudstones, shales, or shaley (highly compacted)sands. In one or more embodiments, a hydrocarbon-bearing zone includesheavy oil in addition to sand, clay, or other porous solids.

The term “jet pump,” as used herein refers to any apparatus having anozzle or nozzles configured to flow a fluid (e.g. a power fluid)through the nozzle such that: 1) the fluid is introduced into a producerpipe at a velocity higher than a natural velocity of the dense slurryflowing into the producer pipe without the jet pump; 2) the fluid flowcreates a low pressure region in a subsurface formation adjacent to thejet pump that has a lower pressure than the formation's naturalpressure; and 3) dilutes the dense slurry in the pipe to a density lowerthan the natural density of the formation.

The term “overburden” refers to the sediments or earth materialsoverlying the formation containing one or more hydrocarbon-bearingzones. The term “overburden stress” refers to the load per unit area orstress overlying an area or point of interest in the subsurface from theweight of the overlying sediments and fluids. In one or moreembodiments, the “overburden stress” is the load per unit area or stressoverlying the hydrocarbon-bearing zone that is being conditioned and/orproduced according to the embodiments described.

The terms “preferred” and “preferably” refer to embodiments of theinventions that afford certain benefits under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the inventions.

The terms “substantial” or “substantially,” as used herein, mean arelative amount of a material or characteristic that is sufficient toprovide the intended effect. The exact degree of deviation allowable mayin some cases depend on the specific context.

The definite article “the” preceding singular or plural nouns or nounphrases denotes a particular specified feature or particular specifiedfeatures and may have a singular or plural connotation depending uponthe context in which it is used.

DESCRIPTION OF EMBODIMENTS

Referring now to the figures, FIG. 1 is process flow chart for methodsof producing a dense slurry in accordance with certain aspects of thedisclosure. The process 100 includes reducing 104 a pressure at aproducer pipe opening (e.g. inlet) to draw a dense slurry into theproducer pipe, wherein the pressure is reduced using a jet pump directedtowards the producer pipe inlet, generating 106 a diluted dense slurryusing the jet pump, flowing 108 the diluted dense slurry into theproducer pipe at an initial flow rate, and lifting 110 the diluted denseslurry through the producer pipe utilizing a slurry lift apparatus. Theprocess 100 may also optionally include conditioning 102 the subsurfaceformation to form the dense slurry and separating 112 bitumen from thediluted dense slurry.

The step of reducing 104 the pressure at the producer pipe inlet may beaccomplished by positioning the jet pump below the producer pipe andinjecting a power fluid through the jet pump into the producer pipe.This approach creates a low pressure region around the producer pipeinlet, which draws the dense slurry into the producer pipe inlet. Thislow pressure region is configured to overcome frictional and compressionsand resistance and draws the dense slurry into the well. Concurrently,the jetting action generates 106 a diluted dense slurry (e.g. lowers thesolids concentration of the dense slurry) by mixing the dense slurrywith a power fluid and pushes or flows 108 the diluted dense slurry upthe producer pipe towards the surface. However, the jet pump will notgenerally be sufficient to push or flow the diluted dense slurry all theway to the surface.

The step 104 may be optional when the radial pressure gradient will beenough to circumvent frictional resistance of the in-situ slurry. Inthis case, dilution 108 of the slurry is the only necessary step,without the need to create a low pressure region. Accordingly, a lowerpower jet pump flow rate may be used. As the frictional resistance ofthe slurry may change during production due to different oil or tar sandquality or different formation impurities (shale, shaley etc.), thepower flow rate of the jet pump may be decreased or increased as needed.

The diluted dense slurry is then lifted 110 by a slurry lift apparatusthrough the remaining portion of the producer pipe up to the surface.The slurry lift apparatus may be any type of device capable of supplyinglift energy to the diluted dense slurry sufficient to lift the slurry tothe surface while overcoming erosion problems. In one exemplaryembodiment, the slurry lift apparatus is a fluid lift apparatus.Alternatively, the slurry lift apparatus is a progressive cavity pump.

In one alternative embodiment, the jet pump may be fitted with anadditional array of nozzles providing additional fluidization. Theseadditional jets may use its own pump or connected to main power fluid ofthe jet pump. The purpose of these jets is by action of fluid jettingdilute sand before it is drawn into well by main jet pump. Diluted sandoffers less resistance thus reducing power fluid flow rate in the mainjet pump. Motive or power fluid may be supplied via a separate pipeusing a surface pump. In certain embodiments of the disclosed process,the power fluid may be selected from the group consisting of water, ahydrocarbon solvent, a heated fluid, and any combination thereof

Another alternative embodiment includes the use of cavitation. Inparticular, the temperature of motive or power fluid coming through thearray of nozzles may be increased and hot fluid can be utilized toinduce cavitation in a mixing chamber for enhanced dense slurryconditioning and erosion reduction. In a jet pump, cavitation occurswhen the pumped power fluid stream velocity is increased to a pointwhere the power fluid pressure becomes very low or near absolutezero--lower than the vapor pressure of the fluid itself--where the fluidstream exits the nozzle. Since higher temperature fluid has a highervapor pressure, it is easier to induce cavitation in higher temperaturefluids, but higher temperature is not necessary. As the power fluidexits the nozzle at this high velocity, the ultra low fluid pressurecauses the power fluid to create cavitation vapor bubbles, which quicklyform and then collapse as the power fluid is recaptured by the throat.This action is extremely violent and causes severe mixing of the powerfluid and the dense slurry being drawn in. The severe mixing actionforces the sand particles or other solids to be fully immersed in thefluid stream and lessens the sand particles' exposure to the throatsurface. Cavitation also helps condition the dense slurry to separatebitumen from the sand particles and mix the dense slurry to form awell-mixed diluted dense slurry.

It should be noted that the disclosed process 100 is considered to becompatible with any and all known bitumen extraction and treatmentprocesses, such as the Clarke hot water extraction (CHWE) and cold waterextraction (CWE) processes, paraffinic froth treatment (PFT) andnapthenic froth treatment (NFT) processes, and others. Such processesare generally known in the art. It is within the scope of the presentdisclosure to modify the process 100 to enhance the performance of suchextraction and treatment processes by methods configured to result in a“well conditioned” slurry. The term “well conditioned slurry,” as usedherein means: bitumen separated from the sand and enter the water phasein the form of small “flecks,” wherein some bitumen flecks are coalescedand attached to air bubbles entrained by power fluid.

Several exemplary process modifications configured to optimizeextraction and treatment processes include: 1) adjusting the flow rateof the power (motive) fluid to control the composition (e.g. sandconcentration) of the diluted dense slurry, 2) adding a chemicalhydrocarbon solvent to the power fluid jet pump and/or complimentarynozzles to precondition the dense slurry to facilitate separation 112 ofthe sand, water, and bitumen, and 3) selecting a type of fluid and afluid pressure to operate the fluid lift apparatus and promote moreefficient extraction and treatment of the diluted dense slurry.

In one particular embodiment, the step of lifting 110 the diluted denseslurry includes injecting compressed fluid into the producer pipe. Inone embodiment of the fluid lift arrangement, the compressed fluid maybe introduced just above the jet pump via a standard side pocket valve.Alternatively, the compressed fluid may be mixed with the power fluid inthe power fluid feed pipe used to feed the jet pump. This alternativeapproach may save some cost and effort on installation, but may alsoreduce the efficiency of the jet pump as additional work would berequired to compress/decompress the gas in the mixing chamber. Incertain embodiments of the present invention, the compressed fluid maybe any one or a combination of natural gas, methane, carbon dioxide,air, nitrogen, tail gas, and products of combustion.

In an alternative embodiment, the step of lifting 110 the diluted denseslurry includes one or both of a progressive cavity pump (PCP) and anelectric submersible pump. In this case, the additional conduit forcarrying compressed fluid would be eliminated. However, the erosion ofthe stator due to high sand flux would require monitoring, the integrityof the elastomer on the rotor of the PCP, and the accumulation of sandabove the pumps may result in drive torque increase, which coulddecrease the efficiency of the system.

FIG. 2 illustrates one exemplary embodiment of the artificial liftsystem used in the process of FIG. 1. As such, FIG. 2 may be bestunderstood with reference to FIG. 1. The system 200 includes a wellbore202 in a subsurface formation 203 having a producer pipe 204 including aslurry input orifice 205, a mixing chamber 209, a diffuser 215, a jetpump apparatus 206 in the wellbore 202 comprising a power fluid conduit207 configured to deliver power fluid 208 to a power fluid nozzle 216and (optionally) additional nozzles 218, and a fluid lift apparatus 210in the wellbore 202 comprising a compressed fluid conduit 211 configuredto deliver compressed fluid 212 into the producer pipe 204 through aside pocket valve 213. The conduits 204, 207, and 211 are held in thewellbore 202 with a triple production packer 214. In a detail view 224,a gas bubble 224 a produced by the fluid lift apparatus 210 is shown asit lifts a slurry slug 224 b generated and flowed by the jet pump 206.

In the exemplary system 200, the power fluid jet 216 injects fluid intoinlet 205 of the mixing chamber 209 creating a lower pressure at 205.The power fluid then mixes with the surrounding fluid (slurry) in themixing chamber 209 and slows down further downstream as pressureincreases in the diffuser 215. The diameter of the mixing chamber 209must be larger than the jet 216 inlet diameter for the jet pump 206 towork.

It should be understood that the power fluid may be provided using apump located at the surface. The pump power and speed may be controlledand monitored at the surface using equipment and techniques known in theart. Similarly, the compressed fluid may be provided to the fluid liftapparatus via a pump or other pressurized fluid system located on thesurface. Monitor and control may also be provided at the surface.

In particular cases, the lift fluid may be a gas such as, for example,nitrogen, air, flue gas, and combinations of these, but may also includesome liquids. In any case, the lift fluid should be configured to beless dense than the dense slurry and the diluted dense slurry and insome cases, expand as it moves up the production pipe 204. The powerfluid may be water, a hydrocarbon solvent, a heated fluid, andcombinations of these. In particular, the power fluid is preferablyconfigured to create a low pressure volume for drawing in dense slurry,decreasing the solids concentration in the dense slurry, and improvingthe conditioning of the diluted dense slurry as the diluted dense slurryflows into and up the producer pipe 204.

Note that the side valve 213 should be appropriately designed to handleincreased erosion from slurry stirred by the gas next to the valveentrance to the producer pipe 204. The system 200 may even includeredundant or alternative valves 213 (not shown) in the event of failureto avoid a costly work-over. Injected gas is expected to form a bubbleand rise up the pipe 204 forming large elongated bubbles 224 aintermingled with slurry slugs 224 b. Such flow is called “slug flow.”

In general, as bubbles 224 a move up, their volume will increase due tothe expected pressure decrease. The larger bubbles 224 a will accelerateand push slurry slugs 224 b faster. Turbulence is expected to increasein such accelerated slurry slugs 224 b. Beneficially, this is expectedto lead to improved conditioning of the slurry due to increased shear ofparticles. One side effect of such acceleration will be an increase infriction losses. As such, appropriately large producer pipe 204 diametershould be chosen to keep frictional pressure loss minimal. On the otherhand, increased producer pipe 204 diameter will warrant a large gas flowrate so an optimum producer pipe 204 diameter should be determined. Inone exemplary embodiment, it is expected that a producer pipe 204diameter of from about 0.1 to about 0.6 meters or about 0.1 to about 0.4m is desirable. However, in some embodiments, it is beneficial to make amore precise determination of optimum diameter based on the conditionsof the subsurface formation, depth, expected diluted dense slurry flowrate, composition of the diluted dense slurry, and other factors asdisclosed in the commonly assigned, concurrently filed applicationentitled “ARTIFICIAL LIFT MODELING METHODS AND SYSTEMS.”

FIG. 3 illustrates an alternative exemplary embodiment of the artificiallift system of FIG. 2. As such, FIG. 3 may be best understood withreference to FIGS. 1 and 2. FIG. 3 depicts a system 300 having anadditional slurry dilution conduit 302 with a valve 304 configured tocontrol and permit flow of power fluid from the power fluid conduit 207to the producer pipe 204. The dilution conduit 302 replaces theadditional nozzles 218 of system 200, but a system may be designedhaving both features and a possibility of switching operation from onefeature to the other feature, depending on the operationalcircumstances. The system 300 is a possible lift design for a shallowreservoir, such as a reservoir at a depth of from about 250 feet toabout 1,000 feet or less. Such a shallow reservoir may have a relativelysmall Bottom Hole Pressure, which could result in a more dense slurryflowing into the producer pipe 204. In such a situation, fluid lift maynot be feasible, warranting further slurry dilution inside the producerpipe 204 via the dilution conduit 302.

Additionally or alternatively, the system 300 may be operated byswitching valve 304 to redirect fluid flow between the power nozzle 216and the conduit 302. For example, as introduced above, there may betimes during production when the low pressure region is not needed dueto decreased frictional resistance. Under such circumstances, the valve304 may be adjusted to direct dilution fluid flow into conduit 302 todilute the flow without concern for the pressure in the region of theinlet. In the event that the production rate of oil sand drops due toincreased flow resistance, the fluid flow may be redirected towards jetpump 206 by adjusting valve 304.

FIGS. 4A-4C illustrate three additional exemplary embodiments of theartificial lift system of FIG. 2. As such, FIGS. 4A-4C may be bestunderstood with reference to FIGS. 1 and 2. FIGS. 4A-4C present threepossible completion designs for the producer well 202. Note that thedesigns of FIGS. 2 and 3 include three pipes 204, 207, and 211 runningthrough a triple packer 214 located in the well bore 202. FIG. 4Aillustrates a system 400 where the compressed fluid conduit 402 ispositioned concentrically around the production pipe 204 with thecompressed fluid being supplied through an annulus formed between thecompressed fluid conduit 402 and the production pipe 204. Note that thepacker 406 is a double packer.

FIG. 4B illustrates a system 420 having a power fluid conduit 422located concentrically through the production pipe 204 and a singleproduction packer 424 with the wellbore casing reaching below the jetpump 206 and producer pipe and having perforations 447 to permit thepassage of slurry while protecting the jet pump 206 from damage orclogging by large rocks that may impinge on the jet pump 206.

FIG. 4C illustrates a system 440 having a power fluid conduit 442 and acompressed fluid conduit 444 in a concentric configuration with respectto each other, but offset from the production pipe 204 and having adouble production packer 446.

FIGS. 5A-5B illustrate alternative exemplary embodiments of theartificial lift method of FIG. 1 and system of FIG. 2 utilizing pumps toprovide slurry lift. As such, FIGS. 5A-5B may be best understood withreference to FIGS. 1 and 2. In particular, FIG. 5A shows a system 500including a wellbore 202 in a reservoir 203 having a jet pump system207, 208, 216 and a producer pipe 204 with a progressive cavity pump(PCP) 502 incorporated therein. The PCP 502 includes a stator 504, arotor 506, and a drive string 508.

In particular, the PCP 502 is what is known as a positive displacementpump (PD pump), which utilizes reciprocating displacement motion to pumpfluids or slurries.

Although some have reported that the maximum volume pump rate of a PCPis about 1,000 m³/day, it may be possible to significantly increase thisrate if the slurry is sufficiently diluted and treated such that erosionof the internal parts (e.g. the stator 504, and the rotor 506) ismitigated.

In FIG. 5B, a system 520 is shown having a rotordynamic pump (RP) 522 inplace of the positive displacement pump 502. RP's are radial typemachines that use a bladed impeller to push slurry and are generallyused to handle higher flow rate, lower head applications. However, RPshave a well adapted version in oil industry called an electricsubmersible pump (ESP). ESP's generally have lower solid handlingcapability than PD pump's and fluid lift apparatuses, but somemodifications into ESP design may improve its solid handling capabilityand, like with the PD pump, dilution and conditioning of the diluteddense slurry may be modified to allow such a pump to operate atsufficient volumetric pumping rates.

In one exemplary embodiment, assembly of system 200 will likely includethree steps: first, installation of production pipe 204 together withconnected short fragments of compressed fluid conduit 211 and powerfluid conduit 207; second, install the triple packer 214; third, connectthe fluid conduit 211 and power fluid conduit 207 with preinstalled pipefragments. All four designs 200, 400, 420, 440 must account forsignificant vertical and radial stresses acting on the lowermost part ofthe well bore 202. Such loads are created by increased overburden loaddue to overburden relief in the reservoir 203 to make the sand flow as adense slurry. Use of slip joints on the conduits 204, 207, and 211 mayat least partially alleviate this problem. Additionally, screwing andunscrewing production pipe of such large diameter (e.g. during aworkover or installation operation) may create leak problems and largehoop stress.

Each design 200, 400, 420, 440, 500, and 520 has its merits anddisadvantages. For example, the system 200 will likely use less steelthan system 400 due to its smaller pipe thickness. System 420 may beless complex to install (due to use of a single production packer 424)than the other designs, but results in a reduction of slurry flow areathrough the production pipe 204 and a consequent erosion increase forboth the inside of the production pipe 204 and the outside of the powerfluid conduit 422. System 440 will use more steel than that of system200, but less than system 400 and will be more complicated to installthan system 420, but avoid the erosion problem due to slurry flow area.Systems 500 and 520 will eliminate the need for a fluid deliveryconduit, but may require some operational limitations and/or have a morelimited performance envelope than the other options. However, it isbelieved that under certain conditions, the presently disclosedembodiments are all capable of improving slurry artificial lift to helpproduce oil sands from subsurface formations.

Each completion design 200, 400, 420, 440, 500, and 520 may have aninlet jet pump being lower than the bottom of the wellbore shoe (e.g.FIGS. 2, 3) or above the wellbore shoe (e.g. FIGS. 4A-C and 5A-B). Inparticular, designs with the jet pump below the wellbore shoe offereasier access to the surrounding slurry, while above-the-wellbore shoedesigns accompanied by wellbore casing slots (e.g. 447) ensuresprotection against large stones and other debris from entering the jetpump 206. Such debris can be drawn by converging slurry and may damagethe completion. Note that the wellbore may extend to the bottom of thereservoir.

EXAMPLES

In one exemplary embodiment, the dense slurry entering the producer pipe204 will be diluted from about 60% to below about 40% sand concentrationand partially conditioned (e.g. by adding solvent, by turbulence due tothe fluid lift system, or some other means). The hydrostatic pressuregradient corresponding to such a slurry is about 1.7 pounds per squareinch per meter (psi/m). The jet pump 206 works with the fluid liftapparatus 210 to produce this pressure gradient to lift the diluteddense slurry to the surface for further processing (e.g. extraction andtreatment processes).

Reservoirs intended for the disclosed methods and systems can be shallow(about 250 feet to about 750 ft) or deep (about 500 ft to about 1,500ft) and even as deep as 3,000 ft. Depending on depth and Bottom HolePressure, different combinations of lift methods of slurry in theproducer pipe 204 may be utilized. Because density of the slurrydownstream of the jet pump 206 is still about 1.5-1.7 times that ofwater, the gas undergoes significant pressure drop while rising fromdeep reservoir. Consequent gas expansion may lead to a significantincrease in gas and slurry rising speed which may incur significantfriction losses. Another consequence of significant gas expansion is anundesirable flow regime transition which may cause significant pressurepulsations in the producer pipe 204.

While the present disclosure may be susceptible to various modificationsand alternative forms, the exemplary embodiments discussed above havebeen shown only by way of example. However, it should again beunderstood that the disclosure is not intended to be limited to theparticular embodiments disclosed herein. Indeed, the present disclosureincludes all alternatives, modifications, and equivalents falling withinthe true spirit and scope of the appended claims.

1. A method for producing a dense slurry, comprising: reducing apressure at a producer pipe inlet to draw the dense slurry into aproducer pipe from a subsurface formation, wherein the pressure isreduced using a jet pump to direct a power fluid towards the producerpipe inlet at an initial flow rate; mixing the power fluid and the denseslurry utilizing the jet pump to form a diluted dense slurry; flowingthe diluted dense slurry into the producer pipe at the initial flowrate; and lifting the diluted dense slurry through the producer pipeutilizing a slurry lift apparatus.
 2. The method of claim 1, wherein theslurry lift apparatus is a fluid lift apparatus utilizing a lift fluid,wherein the lift fluid is less dense than the diluted dense slurry. 3.The method of claim 2, wherein the lift fluid is a gas.
 4. The method ofclaim 1, wherein the slurry lift apparatus is selected from the groupconsisting of a progressive cavity pump, and electric submersible pump,and any combination thereof
 5. The method of claim 1, further comprisingconditioning the subsurface formation to form the dense slurry.
 6. Themethod of claim 1, wherein the jet pump comprises an array of spraynozzles to further dilute the dense slurry or the diluted dense slurry.7. The method of claim 3, the jet pump comprising a power fluid conduitand the gas lift apparatus further comprising a compressed fluidconduit.
 8. The method of claim 7, wherein the compressed fluid conduitis configured in a manner selected from the group consisting of:adjacent to each of the producer pipe and the power fluid conduit,concentric with the producer pipe and adjacent to the power fluidconduit, concentric with the power fluid conduit and adjacent to theproducer pipe, and concentric with each of the producer pipe and thepower fluid conduit.
 9. The method of claim 1, wherein the dense slurrycontains from about thirty volume percent (30 vol %) to about 65 vol %sand concentration.
 10. The method of claim 1, wherein the diluted denseslurry is lifted at a rate of between about 200 cubic meters per day(m³/d) to about 3,000 m³/d.
 11. The method of claim 1, wherein thediluted dense slurry contains from about twenty-five volume percent (25vol %) to about 50 vol % sand concentration.
 12. The method of claim 1,wherein the diluted dense slurry is lifted at least about 250 feetthrough the producer pipe.
 13. The method of claim 1, wherein theproducer pipe has an inner diameter of from about 0.1 meters (m) toabout 0.4 m.
 14. The method of claim 1, further comprising separatingbitumen from the diluted dense slurry.
 15. The method of claim 5,wherein conditioning the subsurface reservoir comprises a fluidizedin-situ reservoir extraction (FIRE) process.
 16. The method of claim 1,wherein the power fluid is selected from the group consisting of water,a hydrocarbon solvent, a heated fluid, and any combination thereof 17.The method of claim 3, wherein the gas is selected from the groupconsisting of nitrogen, air, flue gas, and any combination thereof 18.The method of claim 1, wherein the jet pump is operated to inducecavitation in the diluted dense slurry to increase the mixing of thepower fluid and the diluted dense slurry.
 19. A system for producinghydrocarbons, comprising: a well bore containing a producer pipeextending through an overburden below a surface of the earth into an oilsand reservoir, the producer pipe having at least one opening configuredto permit the flow of a dense slurry into the producer pipe from the oilsand reservoir; a jet pump incorporated into the well bore configured toinject a power fluid at a rate sufficient to generate a low pressureregion around the at least one opening of the producer pipe to draw thedense slurry from the oil sand reservoir into the producer pipe anddilute the dense slurry to form a diluted dense slurry; and a slurrylift apparatus configured to lift the diluted dense slurry through theproducer pipe towards the surface of the earth.
 20. The system of claim19, wherein the slurry lift apparatus is a fluid lift apparatusutilizing a lift fluid, wherein the lift fluid is less dense than thediluted dense slurry.
 21. The system of claim 20, wherein the lift fluidis a gas.
 22. The system of claim 19, wherein the slurry lift apparatusis selected from the group consisting of a progressive cavity pump, andelectric submersible pump, and any combination thereof
 23. The system ofclaim 19, further comprising a fluidized in-situ reservoir extraction(FIRE) system for conditioning the oil sand reservoir.
 24. The system ofclaim 20, the jet pump comprising a power fluid conduit and the gas liftapparatus further comprising a compressed gas conduit.
 25. The system ofclaim 24, wherein the compressed gas conduit is configured in a mannerselected from the group consisting of: adjacent to each of the producerpipe and the power fluid conduit, concentric with the producer pipe andadjacent to the power fluid conduit, concentric with the power fluidconduit and adjacent to the producer pipe, and concentric with each ofthe producer pipe and the power fluid conduit.
 26. The system of claim23, the jet pump further comprising an array of spray nozzles configuredto further dilute the dense slurry.
 27. The system of claim 23, furthercomprising an additional slurry dilution conduit configured to permitflow of power fluid from the power fluid conduit to the producer pipe.28. The system of claim 19, wherein the power fluid is selected from thegroup consisting of water, a hydrocarbon solvent, a heated fluid, andany combination thereof
 29. The system of claim 19, wherein the denseslurry is lifted at a rate of between about 200 cubic meters per day(m³/d) to about 3,000 m³/d.
 30. The system of claim 19, wherein thediluted oil sand slurry is lifted at least about 250 feet through theproducer pipe.
 31. The system of claim 19, wherein the producer pipe hasan inner diameter of from about 0.1 meters (m) to about 0.4 m.
 32. Thesystem of claim 19, wherein the dense slurry contains from about thirtyvolume percent (30 vol %) to about 65 vol % sand concentration.
 33. Thesystem of claim 19, wherein the diluted dense slurry contains from abouttwenty-five volume percent (25 vol %) to about 50 vol % sandconcentration.
 34. The system of claim 19, wherein the jet pump isoperated to induce cavitation in the diluted dense slurry to increasethe mixing of the power fluid and the diluted dense slurry.
 35. Themethod of claim 1, wherein the flow can be redirected between the jetpump nozzle and a conduit opened into the well.